BOSTON -- The youthful Atlanta Hawks are starting to grow up.
"We needed to beat a good team on the road for our confidence level," Atlanta coach Mike Woodson said. "I think that's the best team in the East. Tonight we matched them from beginning to end. From a defensive standpoint, we finally stepped up and played 48 minutes defensively."
Looking similar to the upstart Hawks that pushed Boston to seven games in the opening playoff series in 2008, Atlanta looked poised in its half-court offense, converting against the league's best defensive team.
The difference was in that series, the Hawks couldn't win in Boston. The Celtics took all four games in Boston and went on to win the NBA title.
"Since Day One, we've believed," Johnson said. "Nobody's believed in us. We've been playing pretty good on the road this year."
"We tried to turn it up and put a little pressure on them, but I give all the credit to them," Boston's Kevin Garnett said.
Josh Smith scored 14 and Horford had 12 points and 13 rebounds as the Hawks (7-2) continued their strong start this season, sending Boston to its second straight Friday night home loss.
Last week, Phoenix gave Boston (8-2) its first loss of the season after a 7-0 start.
"It feels great," Josh Smith said. "It always feels good home or away to beat a quality team like the Boston Celtics."
Pierce bruised his knee on a drive to the basket. He sat out the final few minutes of the third, and was wearing a brace and had it taped when he came back early in the fourth quarter.
"It's a little tender," Pierce said. "I'm just going to wait and see how it feels when it cools down. I'm just gonna ice it right now and see how it feels."
Atlanta opened the final quarter with a 10-2 run, pulling to an 82-72 lead on Zaza Pachulia's two free throws with 8:34 to play. The Hawks pushed their lead to 88-76 on Bibby's free throw with 4:44 to go.
Pierce's basket in the lane cut it to 88-80, but Boston never made a threat the rest of the way.
The Hawks, who entered the game fourth in the league in scoring and coming off a win over the Knicks on Wednesday, came out looking to run and controlled the tempo early, jumping to a 14-6 edge in the opening 5½ minutes, before the Celtics tightened up defensively and forced it into a half-court game.
"When you've got a chance to beat a team on the road and you're playing well, everybody looks mature," Boston coach Doc Rivers said.
- Boston F Brian Scalabrine was back in uniform after missing Wednesday's win over Utah with back spasms.
- Red Sox DH David Ortiz was seated courtside and got a big cheer when he was shown on the Jumbotron.
- Perkins was whistled for a technical for throwing an elbow after scoring a basket in the fourth quarter.